Low temperature storage facilities for liquefied gases



A ril 7, 1964 l. v. LA FAVE ETAL LOW TEMPERATURE STORAGE FACILITIES FOR LIQUEFIED GASES Filed Jan. 11, 1960 2 Sheets-Sheet 1 April 1964 l. v. LA FAVE ETAL 3,127,750

LOW TEMPERATURE STORAGE FACILITIES FOR LIQUEFIED GASES Filed Jan. 11, 1960 2 Sheets-Sheet 2 R0677 07:2".- 5 Jazz fllafzve,

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United States Patent 3,127,750 LOW TEMPERATURE STORAGE FACILITIES FUR LIQUEFIED GASES Ivan V. La Fave, I-Iomewood, and Walter R. Mikesell, In,

Park Forest, 111., assignors to Chicago Bridge & Iron Company, Chicago, 111., a corporation of Illinois Filed Jan. 11, 1960, Ser. No. 1,534 11 Claims. (Cl. 62-45) This invention relates to an improved double-walled tank for the storage of liquefied, normally gaseous materials. It more particularly relates to the structure for supporting the inner storage vessel within the outer shell of a double-walled tank.

In the low temperature storage of liquids wherein normally gaseous materials are maintained in the liquid state at substantially atmospheric pressure and at extremely low temperatures of the order of minus 100 F. and below, double-walled tanks having an inner storage vessel which contains the cryogenic liquid and an outer shell spaced apart and insulated from the inner vessel are generally used. Gases such as methane, having a normal boiling point of about 259 F., oxygen having a normal boiling point of about -298 F., and other industrial gases are advantageously stored in the liquid state at temperatures equal to the boiling point of the cryogenic liquid because of the space and material economies which are provided using liquid storage facilities. Because of the extreme temperature differentials which are encountered, stress problems exist in the design of double-walled storage vessels employed in cryogenic storage service Which are not present in the design of single-Walled structures for use in conventional storage service. One of the problems is the design of a suitable support means for supporting the inner vessel and its contents which relieves stresses induced by thermal contraction of the inner vessel upon cooling from ambient conditions to the storage temperature while at the same time minimizing the amount of heat transferred through the supporting structure into the inner vessel.

One of the factors that (in many types of support structures) tends to increase the stress level to a serious degree is the dimensional changes resulting from thermal contraction of the inner vessel and, to a lesser extent, of the support structure upon loading of the inner vessel with the low temperature liquid which is stored therein. The extent of the stress developed is shown by noting that a spherical storage vessel of 60 feet diameter, made of aluminum and placed in liquid oxygen service at a time when the ambient temperature is 70 F. will contract 2% inches in diameter during the filling phase of the storage cycle. Thus any support structure for the inner vessel must be designed to accommodate to this substantial dimensional change Without overstressing in order to avoid structural failures. According to this invention there is provided a support structure for the inner storage vessel which employs a means for preventing the development of stresses or minimizing their eifect in the support structure ordinarily induced upon thermal contraction as the vessel reaches its service temperature.

FIGURE 1 is a vertical cross sectional view of a double-Walled, spherical, cryogenic, storage tank built in accordance with this invention prior to the application of prestress of the support structure of the inner vessel;

FIGURE 2 is the same type of view of the same vessel after the prestressing of the supporting structure for the inner vessel has been completed but before the cryogenic liquid has been introduced;

FIGURE 3 is an enlarged View of apparatus used in a preferred method of applying the bending prestress hereinafter described; and

3,127,759 Patented Apr. 7, 1964 ice FIGURE 4 is a fragmentary view of another prestressing expedient which can be employed.

Referring to FIGURE 1, there is shown a spherical, double-walled, cryogenic tank as built and filled with a test liquid at ambient temperature. This tank comprises a spherical inner vessel 10 and a spherical outer vessel 11 spaced apart from the inner vessel 10 so as to form an insulating space 12 between the vessel Walls. The inner vessel 10 is supported by a plurality of vertical columns 13 which rest on hearing plates 14. These vertical columns are designed so as to be able to support the load of the inner vessel and either the weight of the test liquid or the weight of the stored cryogenic liquid, which ever has the higher specific gravity, when the columns are not subjected to substantial bending stresses. The outer vessel 11 is similarly supported by a plurality of vertical columns 15 which rest on a horizontal base plate 16 which in turn is supported by concrete or other suitable fixed foundation 17. It should be noted that the inner vessel support columns 13 are positioned within the outer vessel columns 15. In the position shown in FIGURE 1 the support columns 13 are preferably not concentrically located. The vertical axis of each support column 13 is located off center from the axis of the outer support column 15 in a direction outwardly from the center of the vessel and preferably in a radial direction. The inner column base plate 14 rests upon and is supported by the outer column base plate 16 which is secured to the foundation 17 by suitable tie bolts not shown. Base plate 14 is not joined to base plate 16 but is adapted to slide thereon provided sufficient force is applied to the base plate 14 to cause such sliding to occur.

After the cryogenic Vessel has been completed as shown in FIGURE 1, it will usually be tested by filling with water or some other suitable liquid having a specific grava ity preferably above that of the cryogenic liquid for which the vessel is designed, said test liquid normally being at ambient temperature. The inner vessel columns 13 must therefore support in compression the weight of the test liquid and the weight of the inner vessel.

Upon completion of the test at ambient temperature the test liquid T is Withdrawn from the tank and a sufficient force is applied to each of the inner vessel columns 13 to displace the base inwardly a distance AR, where AR is the difference between the radius of the inner vessel at the storage temperature of the cryogenic liquid for which it is designed and at the ambient temperature. The displacement is elfected by a suitable force applicator such as a jacking means 18 shown schematically in FIGURES 1 and 2. It is preferred that the force be applied at the base plate 14; however, the desired displacement can be accomplished by applying a suitable force at other positions along the inner support columns 13. This displacement of each of the inner support columns 13 induces a bending moment in these columns 13 which remains until the inner storage vessel 10 begins to be cooled by the introduction of the cryogenic liquid when the vessel is placed in service. As the cryogenic liquid cools the inner vessel the radius of the inner vessel is reduced through thermal contraction by the distance AR as defined above and consequently when the inner vessel 10 has reached the temperature of the cryogenic liquid, the initial bending prestress has been substantially relieved and the inner vessel support columns 13 are once again straight and vertical and not subjected to significant bending stresses. In this condition the inner vessel support columns 13 and the outer vessel support columns 15 can be concentric.

Variations in column design, however, can be used; for example, the outer support columns 15 can be made to intersect the outer vessel tangentially, where the inner support column 13 will not be coaxial with the outer supvalues of (El) and (ED the following formulae are port columns 15. applicable:

In order to keep the amount of heat flowing into the A inner vessel from the outside at a minimum it is necessary V= 1 Z 3 ZZZ 1 Z Z 2 Z 3 to minimize the heat path. Factors which affect the amount 5 1 Q 5 4. 4 12 of heat following a given path lnclude the cross sectional area of the path, the thermal conductivity of the material and comprising the path, and the length of the path. Two of 2 E] the important advantages of the storage tank construction M M of this invention are, first, the absence of a metallic con- U2 nection between the inner vessel and its support structure I l 1 on the one hand, and the outer vessel on the other, except (El f (El 2 4 6 1 at the interface of the base plates 14 and 16, and, sec- 1 1 a 21 1 1 2 1 s ondly, the inner columns 13 are of substantial length. E+T)+ j) 7 The cross sectional area of these columns is kept to a minimum by the prestressing method mentioned above. (G) If the columns were not prestressed in the manner deand:

scribed, then it would be necessary that the columns be M M made stronger in order to withstand both the compressive I 2 stresses resulting from the weight of the inner vessel and The support structure of this invention employs inner its contents and the bending stresses resulting from the support columns 13 which are relatively long and slender. thermal dimensional changes. Thus, by prestressing the Accordingly, the friction between base plates 14 and 16, columns in bending at ambient temperature, but after as compared with the transverse shear attributable to the initial testing, so as to eliminate the bending stresses when stiffness or rigidity of the columns, will be sufficiently the inner vessel has contracted thermally in service, the great when the weight of the inner vessel alone or in cross sectional area of the columns may be reduced and combination with part or all of its contents is being the heat transfer characteristic commensurately improved. supported that the columns will bend and that the base In designing storage tanks employing the column supplates will not slide with respect to one another. For ports of this invention an investigation of the column this reason, it is necessary to accomplish the desired bending stresses and the shear on the base plate is used. sliding by applying outside force in advance of filling When the column is of constant section and of the same with the cryogenic liquid.

material throughout its length, the formulas applicable FIGURE 3 shows in a fragmentary vertical cross secare as follows: tional view a preferred embodiment of the apparatus which 6ECA can be used to displace the base of the inner support col- Column bending stress=- (A) umns 13 in a horizontal direction radially toward the center of the inner vessel 11. In this construction an opening 12E! 20 is provided in the outer support column 15 oriented Base plate shear V= A (B) Z3 radlally outwardly from the center of the inner storage vessel 10, permitting access to the base 14 of the inner support column 13. The inner support column 13 is fas- V=W (O) tened to base plate 14 by welding or other suitable means, where: and an upwardly extending lug 21 is integrally fastened to the base plate 14. Similarly, an upwardly extending jack =Y Modulus of the Column Inflterialpad 22 is fastened to base plate 16. Thus a conventional c=d1stance from the neutral axis of the column to the 5 j k 23 Shown schematically h as a screw jack, extreme fibfir 0f the 6011111111 in the direction of bending draulic jack or scissors jack of suitable capacity, is placed I=IT1OIll1CI1t Of inertia Of the column ill the direction Of between the lug 21 and jack pad 22 and employed as the behdlhgforce applicator. By operating jack 23 to apply a force A di t a deflection 0f the Column through length, to the base plate 14, inner support columns 13 are jacked into the prestressing position. The amount of displacel=1ength the Column, measured from the bottom of ment in the radial direction toward the center of the vessel the shell intersection to the base plate. i AR as previously defined, 9 the haSePhate l f hendlng- FIGURE 4 shows another embodiment of apparatus u=coeflic1ent of friction in shdlng between movable hi h can h d fo l i h b di prcStrc-SS, base Plate and Permanent base p This expedient, being a permanent installation, has the An evaluation f Equations (B) and (C) will give the additional advantage that it is constantly ready and availmaximum shear that can exist between the base plates. for adlustmqnts Whlch Imght deemed necessary The lesser of the two shear values thus obtained will be durmg the P j of the cryogemc Vessel g F the maximum possible shean The maximum possible ample, when it is desired to store another cryogenic liquid moment is then; having an ebullition temperature different than that for V1 which the columns were initially prestressed. In FIG- 13) URE 4 the base plate 14 has two tapped holes 25 and 26 in which threaded rods 27 and 28 extend through holes 29 and the maximum bending stress is: and 30 in the outer support column 15 so as to be engage- Vcl able from the outside with nuts 31 and 32 which, when j (E) rotated in bearing against the wall of the outer support column 15, can accomplish whatever movement of the base If exceeds the allowable bending stress, or if the plate 14 is desired. remaining end deflection of the column, after sliding, is After the prestressing has been accomplished by jacking considered excessive (when (B) equals (0)) prestressing as discussed above, it is desirable to install an insulating of the inner vessel support column should be employed. material in the insulation space between the inner columns The final end deflection can be obtained by equating (B) 13 and the outer columns 15. This insulating material and (C), and solving for A. has been omitted from the drawings as well as conven- In the case of bimetallic columns composed of sections tional piping and fittings employed in filling and emptying l and 1 long (l +l =l), each having respectively the tank, for purposes of clarity.

For the construction of a cryogenic storage tank, materials which do not become embrittled at the service temperatures are selected for the inner vessel and for that portion of the inner vessel support which will have to operate at low service temperatures. The outer vessel on the other hand, and its support structure need not be made of the more expensive low temperature service material because they will operate at approximately ambient temperature and a mild carbon steel is therefore suitable. Materials which may be suitable for the inner vessel and supporting structure include aluminum, stainless steel of the 300 series, and certain nickel steel alloys such as 3 /2% nickel and 9% nickel.

There will be a temperature gradient in the support structure, ranging from approximately ambient temperature at the point of connection of the inner support structure to the outer column or base plate to a low of the operating service temperature at the point of connection of the column to the inner vessel. Because of differences in costs of materials adapted for service at different temperatures, it may be desired to construct the inner vessel and that portion of the inner column which connects to the inner vessel of the more expensive material suitable for the lowest temperature, and to construct all or a part of the remaining portion of the inner column of a less expensive material suitable for an intermediate temperature range between the range for which mild carbon steel and that for which the inner vessel are adapted.

Storage tanks employing the teachings of this invention can be constructed having capacities up to about 60,000 barrels of liquid storage. To illustrate this invention a spherical, aluminum, inner storage vessel of the type shown in FIGURE 1, 60 in diameter for use in liquid oxygen storage at substantially atmospheric pressure, is constructed to be supported substantially concentrically within a 68 diameter outer shell held in elevated position by tubular columns having an ID. of 74". The inner vessel which has a capacity of 20,000 barrels is maintained in position by twelve (12) tubular supports equally spaced about the equator thereof. Each support is 38 to 40 long and is fabricated from l g"ithick aluminum to form 24 ID. pipe. In service each of the inner vessel tubular supports is radially and inwardly displaced 2% inches prior to filling the tank with the liquid oxygen, employing a conventional hydraulic jack having a 15 ton capacity. The prestressing thus induced relieves the stresses in the supports resulting from the thermal contraction of the inner storage vessel produced by the filling of the storage vessel.

It should also be understood that while the preferred embodiment of this invention is a spherical tank such as is shown in FIGURES l and 2, different tank designs can be used employing the instant invention. For example, vertical cylindrical tanks having dished, flat or cone roofs and dished or flat bottoms can have construction features which can take advantage of the prestressing arrangements of this invention for reducing or eliminating stresses en countered in the inner storage vessel resulting from the contraction of the inner storage vessel under service conditions.

From the foregoing description of this invention and the illustrative non-limiting examples, it will be obvious to those skilled in the art that variations may be made by persons skilled in the art without departing from the spirit and scope of this invention. Accordingly, no undue limitations in the claims should be implied because of the speciiic nature of the disclosures shown in this specification.

What is claimed is:

l. A tank for the storage of liquefied, normally gaseous material which comprises an outer shell, an inner storage vessel spaced and insulated from said shell and a plurality of slender inner vessel support columns mounted on said vessel positioning it within said shell, said inner vessel support columns terminating outside of said shell, and a means for applying a bending force to said inner vessel support columns at a location outside said insulated space to prestress said columns whereby bending stresses normally induced in said support columns through thermal contraction of said vessel in being cooled to operating service temperature are minimized.

2. A tank for the storage of liquefied, normally gaseous material which comprises an outer shell, an inner storage vessel spaced and insulated from said shell and a plurality of slender inner vessel support columns mounted on said vessel positioning it within said shell, and a means for applying a bending force to said inner vessel support columns at a location outside said insulated space to prestress said columns whereby bending stresses normally induced in said support columns through thermal contraction of said vessel in being cooled to operating service temperature are minimized.

3. A tank for the storage of liquefied, normally gaseous material which comprises an outer shell, a plurality of hollow tubular columns spaced about and supporting said shell in an elevated position, an inner storage vessel spaced and insulated from said shell, a plurality of slender inner vessel support columns mounted on said vessel positioning it within said shell, each of said support columns being disposed within a cooperating hollow tubular column, and a means for applying a force to said inner vessel support columns at a location outside said insulated space to prestress said columns whereby bending stresses normally induced in said support columns through thermal contraction of said vessel in being cooled to operating service temperature are minimized.

4. A tank for the storage of liquefied, normally gaseous material at substantially atmospheric pressure which comprises an outer shell, a plurality of hollow tubular columns spaced about and supporting said shell in an elevated position, said columns being secured to a suitable foundation having a planar surface within said columns, an inner storage vessel spaced and insulated from said shell, a plurality of slender inner vessel support columns mounted on said vessel positioning it within said. shell, each of said support columns being disposed within a cooperating hollow tubular column, the free end of each of said columns terminating in a planar base plate slidably resting on said foundation planar surface, and a means for applying a force to said inner vessel support columns to prestress said columns whereby bending stresses normally induced in said support columns through thermal contraction of said vessel in being cooled to operating service temperature are minimized.

5. A tank for the storage of liquefied, normally gaseous material at substantially atmospheric pressure which comprises an outer shell, a plurality of hollow tubular columns spaced about and supporting said shell in an elevated positon, said columns being secured to a suitable foundation having a planar surface within said columns, an inner storage vessel spaced and insulated from said shell, a plurality of slender inner vessel support columns mounted on said vessel positioning it within said shell, each of said support columns being disposed within a cooperating hollow tubular column, the free end of each of said columns terminating in a planar base plate slidably resting on said foundation planar surface, and a means for applying a force to said base plates of said inner vessel support columns to prestress said columns whereby bending stresses normally induced in said support columns through thermal contraction of said vessel in being cooled to operating service temperature are minimized.

6. A tank for the storage of liquefied, normally gaseous material which comprises an outer shell, a plurality of hollow tubular columns spaced about and supporting said shell in an elevated position, said columns being secured to a suitable foundation having a planar surface within said columns, an inner storage vessel spaced and insulated from said shell, a plurality of slender inner vessel support columns mounted on said vessel positioning it within said shell, each of said support columns being disposed within a cooperating hollow tubular column, the free end of each of said columns terminating in a planar base plate slidably resting on said foundation planar surface and a jack mounted on said foundation adjacent said base plate and connected thereto for applying a force to the base plates of said inner vessel support columns to prestress said columns whereby bending stresses normally induced in said support columns through thermal contraction of said vessel in being cooled to operating service are minimized.

7. A tank for the storage of liquefied, normally gaseous material which comprises a spherical outer shell, a plurality of hollow tubular columns spaced about and supporting said shell in an elevated position, said columns being secured to a suitable foundation having a planar surface within said columns, a spherical inner storage vessel annularly spaced and insulated from said shell, a plurality of slender inner vessel support columns mounted on said vessel positioning it within said shell, each of said support columns being disposed within a cooperating hollow tubular column, the free end of each of said columns terminating in a planar base plate slidably resting on said foundation planar surface, and a jack mounted on said foundation adjacent said base plate and connected thereto for applying a force to the base plates of said inner vessel support columns to prestress said columns whereby bending stresses normally induced in said support columns through thermal contraction of said vessel in being cooled to operating service temperature are minimized.

8. A method for storing liquefied, normally gaseous material in a storage vessel supported by means of a plurality of support columns positioned about said vessel which comprises prestressing said columns by applying force thereto at ambient temperature sufficient to displace said columns radially inward relative to said storage vessel to relieve bending stresses normally induced in said columns through thermal contraction of said vessel while being cooled to operating service temperature, said force being applied prior to filling said vessel.

9. A method for storing liquefied, normally gaseous material in a storage vessel supported by means of a plurality of support columns positioned about said vessel which comprises prestressing said columns by applying force thereto adjacent the free end of said columns at ambient temperature sutficient to displace said columns radially inward relative to said storage vessel to relieve bending stresses normally induced in said column through thermal contraction of said vessel While being cooled to operating service temperature, saidforce being applied prior to filling said vessel.

10. A method for storing liquefied, normally gaseous material in a spherical storage vessel by means of a plurality of support columns positioned about the equator of said vessel which comprises prestressing said columns by applying force thereto at ambient temperature sufiicient to displace said columns radially inward a distance about equal to the difference in the radius of said vessel when empty and in storage service to relieve bending stresses normally induced in said column through thermal contraction of said vessel while being cooled to operating service temperature, said force being applied prior to filling said vessel.

11. A method in acordance with claim 10 in which said force is applied adjacent the free end of said columns.

References Cited in the file of this patent UNITED STATES PATENTS 2,396,459 Dana Mar. 12, 1946 2,427,676 Horton Sept. 23, 1947 2,467,428 Hansen et al. Apr. 19, 1949 2,495,798 Wissmiller Ian. 31, 1950 2,731,334 Wissmiller et al Jan. 17, 1956 2,926,810 Yeager Mar. 1, 1960 2,981,434 Hawk et al. Apr. 25, 1961 Arresting Officer UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3, 127, 750 April 7, 1964 Ivan V. La Fave et a1.

It is hereby certified that error appears in the above numbered patent requiring correction and that the said Letters Patent should read as corrected below.

Column 5 line 41, for "40" read 40' column 6 line 53, for "positon" read position column 7, line 9 after service" insert temperature column 8, line 26, for "acordance" read accordance Signed and sealed this 13th day of October 1964.

(SEAL) Attest:

ERNEST W; SWIDER EDWARD J. BRENNER Commissioner of Patents 

8. A METHOD FOR STORING LIQUEFIED, NORMALLY GASEOUS MATERIAL IN A STORAGE VESSEL SUPPORTED BY MEANS OF A PLURALITY OF SUPPORT COLUMNS POSITIONED ABOUT SAID VESSEL WHICH COMPRISES PRESTRESSING SAID COLUMNS BY APPLYING FORCE THERETO AT AMBIENT TEMPERATURE SUFFICIENT TO DISPLACE SAID COLUMNS RADIALLY INWARD RELATIVE TO SAID STORAGE VESSEL TO RELIEVE BENDING STRESSES NORMALLY INDUCED IN SAID COLUMNS THROUGH THERMAL CONTRACTION OF SAID VESSEL WHILE BEING COOLED TO OPERATING SERVICE TEMPERATURE, SAID FORCE BEING APPLIED PRIOR TO FILLING SAID VESSEL. 